Industry: Environmental
Instrument: Apollo 9000
Total Organic Carbon Analysis of Particulated Samples
This study includes measurements of total organic carbon (TOC) in samples containing particulates of up to 500 µm particle size using the Apollo 9000. The samples are analyzed without any filtration or pretreatment. The Apollo 9000 utilizes the combustion method for converting carbon into CO2 and a non-dispersive infrared (NDIR) detector for detection of CO2.
Total organic carbon (TOC) analysis grew from the need of industry to monitor the organic loading of its wastewater before discharging them into public waterways. Some of the industry involved here includes chemical processing and hydrocarbon processing, food processing, pharmaceutical, semiconductor and pulp/paper manufacturing. Some of these samples contain large amounts of particulates or sediments. These particulates typically contain significant amount of carbon that is excluded from the analysis when some type of sample filtration is employed in the analysis.
The TOC analysis involves conversion of carbon in the sample to CO2 and detection of CO2 with a non-dispersive infrared (NDIR) detector. The carbon is converted to CO2 by the UV/persulfate method or the combustion method. The high temperature (combustion) method has been the preferred method for samples containing high levels of suspended material or sediments (Method 5310A, 1996).
TOC analysis of a particulated matrix presents a big challenge mainly because of the heterogeneity of the sample. This would lead to bad reproducibility and accuracy, and clogging of lines and valves in contact with the sample. This concern is minimized by letting the sample pass through a filter as stated in Standard Method 5310C. However, as stated earlier, this method excludes the TOC contributed by the particulates that were filtered. The sample preparation is also time-consuming.
Apollo 9000 offers an alternative that includes more accurate measurement of TOC in particulated samples without sample filtration/pretreatment. With the particulate option, particles with 0.8 mm diameter or lower are included in the sampling. Samples containing particulates that have a bigger particle size still need to be homogenized prior to analysis. Due to unavailability of cellulose samples above 500 µm in particle size, this study only includes testing for 20-500 µm cellulose. Homogeneity of the sampling is promoted by magnetic stirring of the sample in the vials during the analysis. Sample testing and conditions are in accordance with the International Standard ISO/FDIS 8245 Annex B (1998) draft. The criteria for the instrument’s ability to measure samples with particulates were based on the ISO/FDIS 8245 method. According to that method, a mean value of 90 – 110 mgC/L and repeatability of < 10% are necessary for a triplicate measurement.
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